JPRN-jRCTs031260249 Imlunestrant Tosylate Breast cancer recurrent Clinical Landscape Report 2026: Design, Endpoints, Sponsor and Readout Outlook

Turn a newly registered trial into a decision-ready landscape. This focused report examines JPRN-jRCTs031260249—A randomized study of Trastuzumab deruxtecan Against Second-line endocrine Therapy In hormone receptor-positive, HER2-low/ultralow metastatic breast cancer (TRANSITION)—using PatSnap Clinical Trials MCP for protocol design and endpoint evidence, Drug & Asset MCP for mechanism and development context, and Company & Deal Intelligence MCP for sponsor background. Explore PatSnap MCP Servers to reproduce the workflow inside an AI research process.

MCP evidence snapshot: 20 July 2026; publication date: 20 July 2026. Trial records can change after the snapshot and should be rechecked before operational decisions.

Why JPRN-jRCTs031260249 is a hot trial to watch

Breast cancer recurrent is increasingly segmented by mechanism, biomarker, treatment setting, geography and endpoint architecture. JPRN-jRCTs031260249 is notable because it evaluates Imlunestrant Tosylate in a Phase 2 design while 無増悪生存期間（PFS）： 主たる解析対象集団を対象とし、無作為化日からPD又は理由を問わない死亡日のうち早い方までの期間とする。効果判定は、Response Evaluation Criteria in Solid Tumors （RECIST） Ver.1.1に準じて評価する。 serves as the main decision variable. The critical question is whether the protocol can convert its rationale into a clinically interpretable and operationally credible readout.

PatSnap Clinical Trials MCP makes protocol fields machine-readable, while the companion asset and organization servers add development-status, target and sponsor context.

Trial landscape snapshot

Design and endpoint interpretation

The phase label is only the starting point. Allocation is Randomized, masking is Open Label, and the intervention model is Parallel Assignment. Planned enrollment of 132 participants across Japan shapes statistical precision, execution risk and external validity. Interpretation should account for baseline risk, prior therapy, assessment schedule, missing-data handling and clinical relevance—not only statistical significance.

• Primary: 無増悪生存期間（PFS）： 主たる解析対象集団を対象とし、無作為化日からPD又は理由を問わない死亡日のうち早い方までの期間とする。効果判定は、Response Evaluation Criteria in Solid Tumors （RECIST） Ver.1.1に準じて評価する。
• Primary: Progression-Free Survival (PFS): In the primary analysis population, PFS is defined as the time from the date of randomization to the earlier of disease progression (PD) or death from any cause. Efficacy will be assessed in accordance with the Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1.
• Secondary: 重点副次評価項目 Global Healthcare Status（GHS）： EORTC-QLQ-C30を用いて測定されたGHSのベースライン（研究薬投与前）から8週時点の変化量とする。 副次評価項目 全生存期間（OS）： 主たる解析対象集団を対象とし、無作為化日から理由を問わない死亡日までの期間とする。 次治療以降での無増悪生存期間（PFS2）： 主たる解析対象集団を対象とし、無作為化日から次治療開始日以降でのPD又は理由を問わない死亡日のうち早い方までの期間とする。 治療成功期間（TTF）： 主たる解析対象集団を対象とし、無作為化日からPDを含む治療中止又は理由を問わない死亡のうち早い方までの期間とする。 次治療開始までの期間（TFST）： 主たる解析対象集団を対象とし、無作為化日から割り付けられた治療の中止後の最初の抗がん後治療の開始日又は死亡日のうち早い方までの期間とする。 奏効割合（ORR）： 主たる解析対象集団を対象とし、最良総合効果が完全奏効（Complete Response: CR）又は部分奏効（Partial Response: PR）が認められた患者の割合とする。 QoL： EORTC QLQ-C30、EORTC QLQ-BR42及び EQ-5D-5L スコアのベースラインからの変化
• Secondary: Key Secondary Endpoint Global Health Status (GHS): The change in Global Health Status (GHS), as measured by the EORTC QLQ-C30, from baseline (prior to study drug administration) to Week 8. Secondary Endpoints Overall Survival (OS): In the primary analysis population, OS is defined as the time from the date of randomization to the date of death from any cause. Progression-Free Survival After Subsequent Therapy (PFS2): In the primary analysis population, PFS2 is defined as the time from the date of randomization to the earlier of the date of disease progression (PD) after the start of the subsequent anticancer therapy or death from any cause. Time to Treatment Failure (TTF): In the primary analysis population, TTF is defined as the time from the date of randomization to the earlier of treatment discontinuation for any reason, including PD, or death from any cause. Time to First Subsequent Therapy (TFST): In the primary analysis population, TFST is defined as the time from the date of randomization to the earlier of the date of initiation of the first subsequent anticancer therapy after discontinuation of the assigned study treatment or the date of death. Objective Response Rate (ORR): In the primary analysis population, ORR is defined as the proportion of patients whose best overall response is complete response (CR) or partial response (PR). Quality of Life (QoL): Changes from baseline in scores of the EORTC QLQ-C30, EORTC QLQ-BR42, and EQ-5D-5L.

Benchmark readouts in the surrounding field

• Netupitant/Palonosetron Hydrochloride and Dexamethasone With or Without Prochlorperazine or Olanzapine in Improving Chemotherapy-Induced Nausea and Vomiting in Patients With Breast Cancer (Phase 3): Cycle 1(Mean) = 4.51 units on a scale (Standard Error, 0.155); Cycle 1(Mean) = 4.93 units on a scale (Standard Error, 0.141)
• A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study of RDX-002 on Postprandial Triglycerides in Patients Discontinuing the Glucagon-like Peptide-1 (GLP-1) Agonists, Semaglutide, or Tirzepatide for the Treatment of Obesity (Phase 2): Incremental Postprandial Triglycerides (TG)(Mean) = 43.81 percent change (Standard Deviation, 92.373); Incremental Postprandial Triglycerides (TG)(Mean) = -51.91 percent change (Standard Deviation, 72.293)
• A Phase II Study to Evaluate the Delay in Ovulation Following Oral Levonorgestrel Plus Meloxicam Compared to Placebo in Obese But Normal Menstruating Women (Phase 2): Interval From First Dose to Evidence of Ovulation.(Mean) = 2.67 Number of days (Standard Deviation, 1.53); Interval From First Dose to Evidence of Ovulation.(Mean) = 4.0 Number of days (Standard Deviation, 0)

These indexed results are contextual benchmarks, not direct head-to-head evidence. Population, treatment line, endpoint definitions, follow-up and analysis sets may differ. Their value is to clarify the type and magnitude of evidence already visible in the competitive landscape.

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Asset and sponsor context

Drug & Asset context: Imlunestrant Tosylate (Approved; ER); Everolimus (Approved; mTORC1 x mTORC2); Exemestane (Approved; aromatase)

Company & Deal Intelligence context: Not reported

The sponsor profile matters because scientific rationale alone does not determine development value. Manufacturing readiness, portfolio fit, geographic reach, partnering capacity and the ability to fund confirmatory development can decide whether a positive signal becomes a competitive asset.

White space around this program

• Sharper patient selection: prospective biomarker or phenotype definitions that identify who is most likely to benefit.
• Clinically interpretable endpoints: outcomes connecting activity with function, symptoms, survival or treatment burden.
• Sequencing evidence: comparative data after the most relevant contemporary standard of care.
• Broader external validity: evidence across additional geographies, demographic groups and real-world settings.
• Operational differentiation: a development path that closes the readout gap without sacrificing safety or durability.

What to monitor next

Monitor recruitment, enrollment changes, protocol amendments, endpoint hierarchy, primary-completion timing, first result indexing, asset ownership and sponsor partnerships. A change in endpoint, population or ownership can alter probability of success before a headline data release.

Bottom line

JPRN-jRCTs031260249 is a focused lens on Breast cancer recurrent development. Its value will be determined by whether Imlunestrant Tosylate can convert the current design into evidence that is clinically meaningful, operationally credible and differentiated from indexed benchmark readouts.

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